The present invention is related to the disclosure shown in U.S. Pat. Nos. 3,112,547 and 3,116,528 in which a grommet having a set of fingers which are expandable by an expander plunger thrust therein, the grommet resisting expansion until a preselected force is applied. For some uses an increased resistance to an expansion force is desirable; however, such increased resistance requires that the grommet be increased in size, requiring a corresponding increase in the size of the opening required.
The present invention overcomes this problem by providing a region axially displaced from the grommet fingers wherein a tubular portion of the grommet is engaged by a portion of the expander plunger capable of radial contraction to produce increased frictional force without altering those portions of the grommet and plunger which enter the grommet receiving opening.